Stability of gaseous volatile organic compounds contained in gas cylinders with different internal wall treatments.

Measurements of volatile organic compounds (VOCs) have been ongoing for decades to track growth rates and assist in curbing emissions of these compounds into the atmosphere. To accurately establish mole fraction trends and assess the role of these gas-phase compounds in atmospheric chemistry it is essential to have good calibration standards. A necessity and precursor to accurate VOC gas standards are the gas cylinders and the internal wall treatments that aid in maintaining the stability of the mixtures over long periods of time, measured in years.

Calibration Strategies for FT-IR and Other Isotope Ratio Infrared Spectrometer Instruments for Accurate δC and δO Measurements of CO in Air.

This paper describes calibration strategies in laboratory conditions that can be applied to ensure accurate measurements of the isotopic composition of the CO in ultradry air, expressed as δC and δO on the VPDB scale, with either FT-IR (in this case a Vertex 70 V (Bruker)) or an isotope ratio infrared spectrometer (IRIS) (in this case a Delta Ray (Thermo Fisher Scientific)). In the case of FT-IR a novel methodology using only two standards of CO in air with different mole fractions but identical isotopic composition was demonstrated to be highly accurate for measurements of δC and δO with standard uncertainties of 0.09‰ and 1.

Ozone Cross-Section Measurement by Gas Phase Titration.

Elevated values of ground-level ozone damage health, vegetation, and building materials and are the subject of air quality regulations. Levels are monitored by networks using mostly ultraviolet (UV) absorption instruments, with traceability to standard reference photometers, relying on the UV absorption of ozone at the 253.65 nm line of mercury.

Methane standards made in whole and synthetic air compared by cavity ring down spectroscopy and gas chromatography with flame ionization detection for atmospheric monitoring applications.

There is evidence that the use of whole air versus synthetic air can bias measurement results when analyzing atmospheric samples for methane (CH4) and carbon dioxide (CO2). Gas chromatography with flame ionization detection (GC-FID) and wavelength scanned-cavity ring down spectroscopy (WS-CRDS) were used to compare CH4 standards produced with whole air or synthetic air as the matrix over the mole fraction range of 1600-2100 nmol mol(-1). GC-FID measurements were performed by including ratios to a stable control cylinder, obtaining a typical relative standard measurement uncertainty of 0.

Accurate Fourier transform infrared (FT-IR) spectroscopy measurements of nitrogen dioxide (NO2) and nitric acid (HNO3) calibrated with synthetic spectra.

A novel method for determining the accuracy of laboratory-based measurements of nitrogen dioxide (NO2) and nitric acid (HNO3) mole fractions using Fourier transform infrared (FT-IR) spectroscopy 1 cm(-1) resolution instruments calibrated with synthetic spectra has been developed. The traceability of these measurement results is to the reference line strength data contained within the high-resolution transmission molecular absorption (HITRAN) database. Incorporating a proper estimate of the uncertainty of this data into the measurement results will ensure that the SI traceable values are encompassed within the uncertainty of the measurement results.

Temperature measurement and optical path-length bias improvement modifications to National Institute of Standards and Technology ozone reference standards.

Unlabelled: Ambient ozone measurements in the United States and many other countries are traceable to a National Institute of Standards and Technology Standard Reference Photometer (NIST SRP). The NIST SRP serves as the highest level ozone reference standard in the United States, with NIST SRPs located at NIST and at many U.S.

Highly accurate nitrogen dioxide (NO2) in nitrogen standards based on permeation.

The development and operation of a highly accurate primary gas facility for the dynamic production of mixtures of nitrogen dioxide (NO(2)) in nitrogen (N(2)) based on continuous weighing of a permeation tube and accurate impurity quantification and correction of the gas mixtures using Fourier transform infrared spectroscopy (FT-IR) is described. NO(2) gas mixtures in the range of 5 μmol mol(-1) to 15 μmol mol(-1) with a standard relative uncertainty of 0.4% can be produced with this facility.